Relays have been used in various applications for many years. A relay is a remotely operated switching device that typically includes a coil and at least one set of contacts providing switched power to a connected device. Based on the power applied to the coil, the contacts change state to turn power on/off to the connected device. When power is applied to the coil, the contacts move to an activated state (this could be opened or closed), and when power is removed from the coil, the contacts move to the default state (this again, could be opened or closed).
A latching relay is a particular type of relay that is also known for use in various applications. Latching relays function differently than a “standard” relay described above in that once the relay changes state, the contacts remain in the last position even when power is removed. So, for example, if power is applied to the coil, the contacts will change state (whether opening or closing). When power is removed from the coil, rather than changing back to a default state, the latching relay will remain in the last state. Only by the application of power to change the state of the contacts again, will the latching relay operate.
Known latching relays typically include a permanent magnet in conjunction with a coil. In order to change the state of the contacts in the latching relay, it is required to change the polarity of the power applied to the coil to offset the flux generated by the permanent magnet. These types of known latching relays are also typically biased by a spring.
One of the problems with standard latching relays is the ability for limited application in high voltage applications. High voltage applications typically are associated with high power transfer and therefore, the switching devices used in these applications must be able to effectively and safely switch even under load. The structure described above (permanent magnet used with a coil) provides limited high voltage interrupting capacity.